Fishermen's News - The Advocate for the Commercial Fisherman

Trawl Visualization and the Future

Trawlers and trawling seems to be in a constant state of change... advancing is perhaps more accurate; fine-tuning. Advances in the materials used in trawl construction are always being considered and new door designs will continually be tried and tested.

A variety of sensors allows the observation of trawl dynamics, door spread, the presence and size of fish and more. Photo courtesy of Simrad.

How Are Advances Made?

The interaction between fishermen and the trawl makers, the door makers and the electronic manufacturers is intense and incredibly valuable. It is rare that something good is made in a vacuum. Inventions perhaps, but advancements require collaboration. This collaboration is as old as trawling, and time proves the concept and design. With sensors, cameras and other instrumentation, the results are very fast. If it works, continue to develop – if the results are bad, then back to the drawing board. Being able to observe the trawl dynamics during actual fishing is a joy to behold from an electronics manufacturer's perspective.

Also driving the interaction is by-catch and the regulations surrounding by-catch. The attitude of the regulators toward the situation has been to allow industry to fix the problem. Placing a hard-cap on a by-catch species and letting the fishermen and the gear makers figure out how to stay under the number is fantastic. This is exactly the approach regulators should take as this is a stimulus for innovation. Everyone in the industry has the same goal; stay under the hard-caps. This increases the freedom of the interaction and innovation between the players and while the regulators are involved, their goal is not to implement and enforce a solution, but simply to enforce the cap.

The speed at which the innovation takes place these days is incredible. Computer design and simulation has been used for some years and this saves time over modeling and flume tank time. The idea flow from the bridge and deck of the fishing vessels to the rest of industry is also a major driving force. All ideas that make it to the water can be confirmed with electronics that measure distances or depth differences, and this is very useful. Cameras are more and more being used to actually see what is going on in situ. Recording, and playback when retrieved, is time consuming but inexpensive if only the cost of the equipment is considered.

There is real value in these cameras, which allow the fisherman to see the situation in real time and allow 100 percent correlation between an action and a reaction. How does the trawl behave during setting, haulback, during a turn? Can a slowdown allow by-catch species a chance to escape? A real time camera answers a lot of the unknowns.

The Current Situation

Currently nothing beats the Simrad FX80 system showing a real time video picture of what is going on, while fishing. Price is of course a consideration. However, once the system is set up and in constant use and everything is routine, a tow without it and not being able to see is sorely missed.

The return on investment is for the fisherman to consider. There certainly are times when the system pays for itself on one tow, particularly when the fisherman is able to abandon the set to avoid a by-catch situation. But there are also times when a set can be finished due to what is seen on the video rather than hauling back as would be indicated by what is showing on the trawl sonar.

Trawl sonars are standard in fisheries with larger vessels. So far real time video is limited to vessels with a by-catch issue and the revenue stream to justify the purchase. However the advances in trawling electronics on the wireless side of the business are also significant and these advances are affordable for all trawlers. What makes these systems affordable is that they are modular in nature. This means that a sensor set for the most critical measurement can be purchased first with additional sensors for the next critical measurements purchased as the revenue stream/need balance is achieved.

Traditionally, door spread is usually considered the most critical measurement. Spread is a key indicator in the amount of water "sifted" and generally the greater the volume of water the greater the amount of fish.

Next is confirmation that fish are going over the footrope. This is actually more than confirmation, it also lets the fisherman know when they run out of fish, at which point a decision is made to keep going or to turn back on to where there were fish. A turn is one of the times during a set that the door roll and pitch need to be watched, those parameters are readily available with most systems.

Depth of doors, depth of headrope and differences in depth between different parts of the trawl are all of interest. As are all and any parameters that can be measured. The ability to visualize the entire trawl is the future.

The Future

Systems in use in the oil industry are being looked at to determine whether these tools can be used to visualize the trawl in a dynamic fashion. Sensors in this case are simply pingers. Pingers give the system their location. The location of each pinger can be shown on a screen in comparison to the other pingers and dozens of pingers can be displayed.

This has tremendous potential, and while this is futuristic in nature the world of 3-D and virtual reality is coming to the fishing industry. The potential problems are known, mostly the potential noise of an active fishing vessel and handling of sensitive equipment on deck. Cost is an issue, always, but only until the concept is proven to have a solid value.

The future of trawling has many paths. By-catch is the driving force. Excluders, grids and diverters are all being worked on with the goal of catching the "right" fish and letting the "wrong" fish swim away without damage or harm. The right or wrong fish is not just the right or wrong species but also size. Factories are set up for a range of sizes and if the delivered fish are too small, fish meal, or returning them to the sea, dead, is sometimes the only answer. Acoustics (echosounders and now some modern sonars) mounted on the vessel have the ability to give the fishermen an accurate size and biomass estimate of the fish seen from the vessel. This technology will come to the trawl given time. The size of the electronics is getting smaller and size is always an issue. Power is another issue and most importantly getting the information up to the wheelhouse in a usable format. Both of these, power down and information up, require a reliable 3rd wire or two. Today all 3rd wire trawl systems are using a quality coax cable. This is considered ancient technology by the rest of the world of underwater, cabled, oceanographic research. Multi conductor and fiber optic cable options are plentiful and with the amount of information coming, and potentially coming, from trawl instrumentation, changes to the acceptable cable are needed. For the new build activity we are seeing these days, it will be important to take the future needs into consideration.

The Path to the Future

Real-time video can be expensive, but offers the ability to abandon a set to avoid a by-catch or finish a set rather than hauling back as would be indicated by the trawl sonar. Photo courtesy of Simrad.

Vessels using the FX80 real time camera system are now installing a third, 3rd wire winch! This is because two 3rd wires are in the water every tow and a backup is always a good idea. This has come about as fishermen are deploying the camera at the cod-end and the trawl sonar is still deployed in the traditional fashion, at the headrope. This is fishermen making decisions on how best to use the tools available to them. One aspect to the development of tools for fishing is that fishermen routinely use a tool for more that the intended purpose. This pushes development.

Advances in materials, particularly durability, are making it easier to take previously fragile instruments and make them "trawling proof". This means all instrumentation in normal use in oceanographic research can reliably be used in fishing. The "link" for this instrumentation is built into the FX80 link. What will be of value to the fishing effort of PH or O2 levels? We don't know – those might be vital, or just interesting, or perhaps an unwanted distraction... time will tell.

Michael Hillers has been with Simrad Fisheries since 1984 and specializes in maintaining the link between the fishermen and the engineering and development teams at the various Kongsberg factories that design and manufacture the fishing acoustics.